The field of the invention is stacking flat or planar food articles. More specifically, the invention relates to counter-stacker devices used to count and stack tortillas.
In the production of flat food products such as tortillas, it is highly desirable to minimize the amount of labor required, since labor costs are a significant portion of the total cost of production. Various counter-stacker devices have been developed to automate the counting and stacking of planar food products or articles such as tortillas and other flat breads. Typically, counter-stackers or similar devices operate using one or more belts to transport the food article to a stacking device.
The stacking device preferably should be able to form a stack of planar food articles (typically cylindrically-shaped). The cylindrically-shaped stack is easier to handle and pack into finished product. Prior art stacking devices have utilized a variety of stacker configurations to stack planar food articles.
U.S. Pat. No. 4,760,777 discloses a tortilla stacker that uses a cylindrical stacking container disposed adjacent to a stack loading conveyor. The individual tortillas are projected from the conveyor into the stacking container.
U.S. Pat. No. 4,006,831 discloses an automatic tortilla counter and stacker that uses alignment arms to aid in forming the tortilla stack.
U.S. Pat. No. 5,763,861 discloses a stacker retainer belt that advances a stacker retainer. The stacker retainer has a semicircular stack retaining member to catch tostada articles from a transporting belt.
U.S. Pat. No. 4,620,826 discloses a vacuum belt system that suspends tortilla articles over a plurality of tines. The tortillas are pushed off of the vacuum belt by a piston mechanism onto the tines located beneath the vacuum belt.
U.S. Pat. No. 3,915,316 discloses a counting and stacking apparatus that uses an arcuate-shaped stacking rack that includes a plurality of vertical tines or rods. When the desired number of articles are stacked on the stacking conveyor against the rack, the rack rapidly retracts to release the stack for discharge.
U.S. Pat. No. 4,530,632 discloses a stacking apparatus that includes a stationary rack formed by a number of rods. As the tortilla drops from a vacuum belt, the tortilla contacts an arcuate aligning member which guides the tortilla as it drops onto the rack.
U.S. Pat. No. 5,253,762 discloses a stacking and counting device that uses a block having a partial cylindrical cut-out and guide to maintain the cylindrical configuration of the stack of tortillas.
Prior art devices have also employed shaking devices to aid in forming product stacks. For example, U.S. Pat. No. 4,054,015 discloses a chip packing apparatus that includes a vibration assembly associated with a cylindrical stacking tube to aid in stacking food chips. U.S. Pat. No. 5,720,593 discloses a shaker unit that shakes and jostles tortillas that are being stacked in a stacker. Similarly, U.S. Pat. No. 6,053,695 discloses a tortilla canister attached to a vibrator to jiggle down any misaligned tortillas.
While these types of prior art devices have performed with varying degrees of success, disadvantages remain. While vibration or shaking of the stacking device can improve stack formation, tortillas are sometimes offset from one another during stack formation.
Another disadvantage related to existing counter-stacker devices is their propensity to jam during operation. When the device becomes jammed, product will accumulate at the jam until the jammed product is removed. Typically, the entire counter-stacker device has to be stopped or paused to remove jammed products. Current counter-stacker devices typically operate with multiple rows or lanes of product. Consequently, if one lane of the counter-stacker device becomes jammed, the other lanes, which are not jammed, must also be stopped or paused. This decreases the overall product throughput for the device.
For example, in the apparatus disclosed in U.S. Pat. No. 4,620,826, if the vacuum belt were to malfunction or if product jammed during stacking, all four lanes (as shown in FIG. 3) would have to be stopped or paused while the device is repaired or the jam is removed. No tortilla products are stacked during this downtime.
Accordingly, there is a need for a device for stacking planar food articles that overcomes these disadvantages. The device should preferably be able to stack food articles on top of one another with little or no offset between different layers of the stack. In addition, the device should preferably operate with multiple lanes and permit individual lanes to be paused or stopped without disrupting the operation of the other lanes.
In a first aspect of the invention, a counter-stacker for stacking planar or flat food articles or products includes an infeed conveyor preferably having a plurality of lanes for containing planar food articles. A vacuum conveyor system is advantageously located adjacent to the infeed conveyor that includes a plurality of vacuum conveyors. Each vacuum conveyor may include a frame, a pair of pulleys rotationally mounted to the frame, a drive shaft coupled to one of the pair of pulleys, a vacuum generator or a connection to an external vacuum source for generating vacuum conditions within the frame, and a vacuum belt mounted to the pair of pulleys. The vacuum conveyor is preferably pivotable about one of the pair of pulleys.
In a second aspect of the invention, the counter-stacker according to the first aspect includes a plurality of catch cups located beneath the vacuum conveyors for stacking the planar food articles. The catch cups are preferably connected to an oscillating mechanism for oscillating the catch cups.
In a third aspect of the invention, the counter-stacker according to the first aspect includes a rejection device. When the vacuum conveyor is pivoted in an up position, a rejection device for the corresponding lane is engaged for rejecting planar food articles from being input onto the corresponding lane of the infeed conveyor.
In a fourth aspect of the invention, a method of stacking planar food articles includes the steps of transferring a planar food article to a vacuum conveyor. The planar food article is then transported to a region located above a catch cup. Oscillating motion is imparted on the catch cup. The planar food article is then dropped into the oscillating catch cup.
In a fifth aspect of the invention, a method of stacking planar food articles in a plurality of lanes includes the steps of feeding planar food articles to an infeed conveyor in a plurality of lanes. The planar food articles are transferred to a plurality of vacuum conveyors, with each vacuum conveyor preferably corresponding to a particular lane. One of the vacuum conveyors is pivoted from a down position to an up position. Next, planar food articles are prevented from being fed to the infeed conveyor at the lane corresponding to the pivoted vacuum conveyor.
It is an object of the invention to provide a counter-stacker that creates improved stacks of planar food articles. It is also an object of the invention to provide a counter-stacker that can continue to count and stack planar food articles during jams and malfunctions of the counter-stacker.
The invention resides as well in subcombinations of the features shown and described.